1. Field of the Invention
The present invention relates to an automatic lighting device which automatically turns on/off a vehicular light in accordance with an external illuminance. The present invention also relates to a method for automatically turning on/off a vehicular light in accordance with an external illuminance.
2. Description of the Related Art
Conventionally, an automatic lighting device (also called a light control system) which detects an illuminance surrounding a vehicle with a sensor and controls vehicular lights in accordance with a detecting illuminance is known (for example, JP-A-2003-291718). For example, in an automatic lighting device in the prior art, an illuminance sensor detects an external illuminance around a vehicle, and an ECU (Electronic Control Unit) turns on vehicular lights including head lamps and tail lamps when the external illuminance is not more than a certain illuminance threshold, and turns off the vehicular lights when the external illuminance is more than the illuminance threshold. In this way, the automatic lighting device turns on the vehicular lights automatically to help a driver when the vehicle enters a tunnel, and when it is getting dark at evening, for example.
A person having a light iris color normally does not need to turn on the vehicular lights until late night because he has an excellent night vision. A person having a dark iris color needs to turn on the vehicular lights even at early twilight because he has a less-excellent night vision.
However, the automatic lighting device in the prior art automatically turns on/off the vehicular lights at a certain external illuminance. Therefore, a timing of turning on/off the vehicular lights at twilight when the surrounding gradually becomes dark is not optimized for driver's physical characteristics such as night vision.